Amplifier system, method, and apparatus



March 29, 1932. s, Y WHlTE AMPLIFIER SYSTEM, METHOD, AND APPARATUS Filed July 22. 1927 Patented Mar. 29, 1932 UNITED STATES PATENT OFFICE.

SIDNEY Y. WHITE, OF N EW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO RADIO 'I CORPORATION OF AMERICA, OF NEW YORK, N. Y., A CORPORATION F DELAWARE AMPLFIER-SYSTEM, METHOD, AND APPARATUS Appneation mea July 22, 1927. seri-.11 No. 207,607.

ie paratus and .a substantial amount of nonselective apparatus. -A further object is to secure a high order of amplification With a minimum of apparatus.

Another object is to secure more or less uniform amplification over a very Wide range of frequenc1es, such as the range employed in rad-io broadcasting.

A still further object is to obtain a very high order of amplification kon acne-frequency basis at high frequency Without ldeveloping the unstable conditions heretofore accompanying such attempts.

Other uses and benefits of my invention will be obvious to those skilled in the art from the following description and accompanyingdrawings, in which Fig. 1 diagrammatically illustrates a simple application of my invention that'lends itself to ready eX- planation. Fig. `2 diagrammatically illustrates another application of unique form to a radio receiver.y Fig. 3 yshows a combination of .uses in a more or less elaborate and highly efficient form of radio receiver. Like reference symbols represent like parts as far 5125 as possible throughout the several figures.

In Fig. 1 a source of more or less Wide range of high frequencyV alternating currents.l indicated as an 4ordinary radio receiving antenna A grounded at G, is shown coupled i@ to the input `electrodes of a three-electrode vacuum tube VT1 through an indicated nonselective impedance I, Which may therefore be a resistance, a condenser, or a so-called choke or capacitivelyreacting coil, and therefore substantially equally non-selective lfor all frequencies ofa `given Wide range of radio frequencies. The tube is indicated as energized for operation from sources +A -B,` *A and -1'fB in amanner too Wellknown to v require explanation,the anode oftube VTi i being energized through a choke coil K to more or less confine high frequency currents to other circuit paths of the system. A second tube VT2-is 'shovvncoupled tothe output circuit of the first tube 4through a variable period circuit LZCZ, Vand a combined electromagnetic :and electrostatic jcoupling including the inductive relation betvveencoils L1 and L2 and the coupling condenser C1, by means of Whichcombined coupling the coupling relation can be controlled in I,any desired manner with frequency, andtherea'ction of the variable "circuit .on the output `circuit `also yso controlled, as more fully described in my copending applications Serial Nos. 48,936 of August 8, 1925, and 49,521,0f August 11, 1925, kpatented :November 4, 1930, No. 1,780,611. The output connections to tube VTZ are not completed as this lpart of the sysem is not required for the present explanalon.

The system as so far described is one in substantial vuse in radio receivers, bein-g commonly termed a coupling tube, and has for one object permitting the design and adjustment of the constants of variable period circuit LQCQ in the factory, and not havingthe circuit thereafter `materially disturbed by Whatever length and disposition of :antenna A the ultimate user of the receiver may employ, as would be the case if the antenna were more or less directly associated with the variable circuit. This precaution is of particular importance in the present day practice of-.providing so-called single dial control for a plurality of such variable circuits 'includedin the same system. It is quite generally recognized that this coupling tube, with its non-selective input, adds nothing to the over-all amplification of p Y ao ternal capacity'of `thetube a'lone,'so that in the system. In fact, it generally imposes a slight loss in amplification over that which would be obtained by efficiently associating the antenna more or less directly With the variable circuit.

It is the purpose of my invention to overcome this difYl'culty such that the coupling tube can be called upon for the additional function of materially and selectively amplifying in spitev of the non-selective coupling impedance, and I accomplish this` result by the simple expedient of connecting the grid lead of coupling tube VTl to a point of suitable potential and polarity invariable circuit L2C2 through condenser C3, it being possible to chooseV the polarity relation between coils L1 and L2 such .that this can be done, which relation happily happens to be that required for the electromagnetic and electrostatic energy transfers in the combined coupling to be assisting, the condition necessary to employing this coupling in itsinvaluable ability to secure uniform results over a remarkably Wide'range of frequencies. In fact Iffind that to attempt to cover the radio broadcast band With any degree of effectiveness without this so-called constant coupling effect would be hopelessly impossible.

By adjusting the .relative values of condenser-C3 and the combined coupling I find that Ican. secure anyY degree of selective` amplification desired, as variable condenser C2 is operated, from below the natural Vamplifying ability Aofthe tube even through to oscillation generation, and byv properly adjusting the combined coupling can keep the degree ofy amplification constant with frequency, or vary-it in any y'predetermined Way. It so happensthat fora .coupling thatvprovides a suitable practical energy transfer from tube VTl to .VT2 I can rely on adjustment of condenser C3 to obtain the degree of amplification desired, so that my addition to the system does not interfere with itsnormal operation. For good radio broadcast receptionI do not recommend an amplification beyond the natural amplification of the tube, this to avoid the distortion thatA accompanies regenerative amplification.

It will be noted that the addition of con-` denser lC3 couples the variableperiod circuit L20/2 somewhat more closely to the antenna system than Would be had through the incaseswhere influences due to varying antenna conditions are important it is desirableto 1nsert a condenser Ciof'more or less small ca- Y pacity initheantenna. Such a condenser Will slightly reduce the efficiency, but With the gain due to making the tube effectively amn plifying this precautioncan vvellbe afforded.

Fig. 2 illustrates an adaptation of my presentY invention' to the invention contained' in my copending application, Serial No. 24,088 of April 18, 1925.`l In that application I provided forlthe use of one of the tubes of the audio frequency portion of a radio receiver as a coupling tube for the radio frequency portion Without any suggestion for securing useful or selective amplification of the radio frequency currents in the audio stage. Fig. 2 such result is had, thereby giving a triple function tothe one tube, namely, audio amplification', coupling tube and selective radio amplification.

i In Fig. 2 tube VT1L is shoWnas thevfirst audio tube ofthe audio system coupledto the radio system including tube VT2 through indicated audio frequency transformer T1, the primaryV of Whichv is shown by-passed ,by the usual condenser C6. The antennar A., vgrounded at G, is shown connected across the secondary of audio transformer T1, Which should preferably have a radio frequency choke K1 in series if the distributed capacity of the secondary does not offersuiiicient reactance.

Thereis thus provided :for audio-tube VT1- a non-selective impedance input for radio frequency currents. The output circuit includes a radio frequency choke l@ if the primaryof audio frequencytransformer T2 does not offer sufficient impedance-*to radio-frequency current flow to make the .choke unnecessary.

The impedance so created in the output circuit forces the radio frequency currents through ythe path including condenser C7 and a coupling, preferably combined electroinagnetic and electrostatic, With variable period circuit LgCg, the radio frequency currents s being thus selectively delivered to tube VT2, Which isindicated as connected fto operate as a rectifier by reason of grid condenserC5,

grid leak R, and lovv anode exciting .potenv tial', all as Well understood in the'art. `The modulations of the rectified radio frequencyV currents are filtered through audio transformer T1, and pass forward Without appreciable opposition from radio frequency choke ,Ki to be amplifiedby tube VTl, and passed on, or otherwiseA utilized, throughV transformer T2. rIhe tubes are indicated as ener-.-

gized in the manner mentioned in connection with Fig. l.

So far as described the Vsystem'is substantially the same as thatof my copending ap- VVplication referredjto. It Will be noted that,

asin the case of' Fig. l, I connecta condenser C3 between the grid lead of the nonselective input tube, in this case the first audio tube, and the variable period circuit 112C2 vWhich is constant coupled to theoutput system of the Vfirst audio tube.` By adtransmission line.y Without such precaution the low frequency disturbances would be impressed directly into the audio amplifying system and be sufficiently amplified to be annoyinof. Using the last audio tube as the coupling tube would aid to minimize Vthis effect.

F ig. 3 shows diagrammatically an arrangement for a radio receiver to obtain an extremely high degree of selective amplification at any one of a Wide range of frequencies, such as a broadcast receiver, embodying for this purpose the present invention as illustrated in both Figs. l and 2, combined electromagnetic and electrostatic coupling for constant coupling and constant amplification control, aswell as the arrangement disclosed in a copending joint application of E. H. Loftin and myself Serial No. 207,618 of July 22, 1927, for securing selective amplification in a system of tWo vacuum tubes linked through a non-selective impedance. It adds the further feature of improvingthe performance of the detector stage tube in a manner to be later described.

The diagram Well illustrates the simplified form to which the system can be reduced and yet contain so many features contributing towards high selective amplification Without operating interferences, and in addition maintain this performance over an extremely Wide band of frequencies `with stable operation and a minimumof variable-period circuits so electrically disposed as not to suier undue vdisturbing influences from each other, the operator or the antenna With which used. Such a receiver is ideally adapted to the severcst of allconstruction problems in radio, namely single dial control.`

'Tube VTl may be any audio frequency stage tube, but is show in Fig. 3 as the'first stage. This tube is so associated with antenna A and variable period circuit LgCg that it selectively amplilies and delivers radio frequency currents to first radio frequency tube VT2 in the manner fully described inl connection With Fig. 2. Tube VTZ is coupled to tube VT3 through non-selective impedance I1, shown as a choke coil, and by reason of the coupling of its output circuit to variable period circuit LEC2 through condenser C3 and combined electromagnetic and electro-- static coupling shown, its plate circuit reactance is selectively controlled with frequency to overcome the capacitive reactance of impedance I1 to cause this tube to selectively amplify the desired signal, as more fully described in the copending application previously referred to, and thus deliver twice selectively amplified desired signal energy to tube VT3. At this point the system of my present'invention, explained in connection with Fig. l, is injected into the system. Tube VT?, has a non-se-lective input in the form of non-selective impedance I1, but a variable cir- Y of selective amplification take place inthem,

thus delivering five times selectively amplified energy to tube VT6 of the detector stage. However, I neednot stop the selective amplilication at this pointl In general the tubes of detecting stages are operated mostinelliciently from the amplifying point of vievv by reason of the audio transformer 1n the output reacting capacitively to the radio frequency currents to produce a capacitiveplate circuit reactance which, acting through the tube capacity, destroys itsamplifying ability; By making` the same connection for tube VTG, through condenser Cg, tothe coupling of the preceding variable circuit (circuit) as Was done for tubes VTZl and VT4, a substantial degree of selective amplificationrcan be injected through the intermediary of the detecting stage tube, thus making six steps of selective radio frequency amplification vpossible with but three variable circuits and four radio frequency tubes perse.

By Way of comparison manufacturers of receivers having three stages of radio frequency amplification of the' type having successive variable circuits linked through tubes, and requiring four such circuits for the three tubes, often claim amplification as high as veight per stage With tubes Whose natural ampliiication average but the eight claimed.

Allowing a coupling and loss Vfactor of certainly` at least 50 such claims, if true, neces- I sarily mean that the tube is `actually amplifying at least 16 times, or is operating on the highly regenerative and critical side of operation. Three stages ofsuch amplication is equal to veight to the third power, or an overall amplification applied to the detector tube of approximately 500. In my system of Fig. 3 I can accept the natural amplification of eight of each tube, and thereby eliminate all regeneration With its distortion and instability, and accepting a loss and coupling factor of 50%, have a net gain of'l per stage, and with the six gaining stages described `the overall amplification Willbe the sixth power of four, or approximately 4000, a ratio of 8 to l in favor of my system operated under less difficult and harmful conditions. NOW since the detector action is'not'directly proportional to Vthe strength of the radio. frequency currents, but as the square, my detected signals under the extremely stable conditions outlined Will be 64: timesas strong as the successive circuit system operated underrdecidedly critical and distorting coni ditions. Furthermore three stages appears to be the practical limit of the successive circuit system with any useful gain per stage. I see no theoretical or practical reason why `with my system the yamplification cannot be carried on indefinitely as long as well known precautions to prevent distant stage feed backs are employed, such as shielding, angulation of coils Yand the like.

The detector stage outputris passed on to the audio systemethrough transformers T1 and T2 in a conventional manner. The tubes arefshown energized in well known conventional manner, choke coils K, K3, K4 andK being used in connection with plate energizing as previously outlined. Condensers CS Y prevent the plate potential from reaching the grids'of tubes VT3 and VTS'. Choke coils K1 and K2 provide conductive grid bias paths around-their respective coupling condensers.` Also the variable condensers of variable circuits 1, 2 and 8 are connected to a common conductor of ground potential,

f satisfying a practical requirement for single dial control, and the high vpotential sides of these three circuits are so generously electrically isolated from each other as to substantially eliminate all'of the difficulty encountered in successive circuit systems where it is the very operation of the succeeding circuit that overwhelmingly controls the am plif'ying ability of the tube to which the preceding circuit is connected.

. No limitations are Vintended by reason of having described my invention in connection with radio receivers.

I claim: 1.7The method of selectively highly amplifyingalternating currents of a maintained one-frequency which comprises selectively amplifying said currents, non-'selectively ceding selective circuits which comprises selectively impressing said currents upon an amplifier, non-selectively transferring ythe 'amplifier output of said currents to the input electrodes of a second amplifier, selectively controlling the amplifying ability of said first amplifier to accord with the selective im pressing of currents thereon, selectively absorbing the energy of the output currents of said second amplifier to accord with the preceding selective amplification in the first amplifier, reimpressing a portionof said abl sorbed energy upon the' input electrodes of y said second amplifier, and repeating theoptrodes of said amplifier, a second amplifier,

a variable period circuit coupled to the output circuit ofsaidamplifier and connected to the input electrodes of said second amplifier, anda condenser connected between the control input electrode'of said amplifier and a point of'such polarity in said variable circuit that a portion ofthe selected fre-V quency energy inv said circuit is transferred to said control electrode whereby the alternating current corresponding to said' se? lect'ed frequency is selectively amplified.

4. A system for amplifyingl alternating currents including an amplifier and means for non-selectively impressing alternating` currents upon the input electrodes thereof, a variable period circuit, a two-element coupling between said variable circuit and the output circuit lof said amplifier, one ofv said elements transferring energy increasingly` with frequency increase and the other of said elements transferring energy decreasingly with frequency increase, said elements being so poled as to' transfer energy in phase, andy means for impressing a portion of the energy selectively absorbed by said' variable period circuit upon the input electrodes of said amplifier. f f

f5. A radio receiverincluding a radio freisoV quency amplifying portion and an audio fre- A i quency amplifying portion, a radio frequency collecting antenna non-selectively vconnected to the input of one of the amplifiers in said audio frequencyrportion, a radio frequency coupling between the output circuit vof said amplifier and a variable period radio frequency circuit in said radio frequency portion, and a radio frequency energy transmitting connection between the input of said audio amplifier and said variable period circuit whereby said audio amplifier is caused to selectively regeneratively amplify radio frequency currents collected on said antenna for delivery through said coupling to said radio frequency portion.

6. A system for the multiple selective am-A plification of alternating currents at a main-V tained one-frequency including an amplifier and means for nonlselectively impressingthe alternating currents upon the input electrodes thereof, means for selectively absorbing energy from the output circuit of said amplifier, Y means yfor delivering. a portion of said selec-V tively absorbed energy to said input elec-k trodes, a secondamplifier kconnected to receive the remainder ofsaidr selectively absorbed energy from said'Y circuit, a non-selective impedance associated with the output circuit of said second amplifier to transfer energy therefrom, and means for altering the reactance upon said output circuit of said non-selective impedance in frequency consonance with the selective absorption of energy from the output circuit of said first amplifier.

7. A system for the multiple selective amplification of alternating currents at a maintained one-frequency including an amplifier, a non-selective impedance coupling said amplifier to asecond amplifier, means causing said first amplifier to selectively amplify said alternating currents-in spite of said nonselective impedance, and means associated with the output circuit of said second amplifier for causing selective amplification therein in consonance with the selective amplification in said first amplifier.

8. A system for multiple repeated selective amplification of alternating currents at a maintained one-frequency without deleterious reaction of succeeding selective circuits on preceding selective circuits including an amplifier, means for selectively impressing said alternating currentsthereon, a second amplifier, a non-selective impedance coupling said amplifiers, means for causing said first amplifier to selectively amplify in spite of said non-selective impedance, a variable lperiod circuit associated with the output circuit of said second amplifier, means associated with said circuit for causing said second amplifier to selectively amplify in consonance with the selective amplification of said first amplifier, and one or more additional such systems receiving initial energy from said variable period circuit to repeat the provided for multiple selective amplification. Y

9. In a system for selected amplification of alternating current of any one frequency over a wide range of frequencies including a pair of multi-electrode electron discharge tubes connected in cascade the method of selecting, amplifying and transferring energy of any one of the desired current frequencies which consists of non-selectively impressing the currents on the input of the first tube, selectively absorbing energy from the output currents of the first tube and impressing it upon the input electrodes of the second tube, and impressing a portion of said selectively absorbed energy on the input electrodes of said first tube.

10. A system for the selection and amplification of any one of the current frequencies of a wide range of frequencies including a multi-electrode space discharge tube, nonselective impedance means for impressing all of the current frequencies upon the input electrodes of said tube, a second tube, a variable period circuittunable over said wide range of frequencies connected across the input electrodes of said second tube and coupled to the output circuit of said rst tube,

onto the input electrodes of said first tube in phase with the energy ,of said Vfrequency'- therein. Y i

ll. AL sys-tem for theselectionandg'amplifi-L 'cation of any oneofthe current'frequencies of a lwidel range of frequencies including a three electrode vacuum tube, non-selective impedance means connected between'thev grid and filament of said tubelfor impressing all of the current frequencies' upon the input electrodes of said tube, a second three elec` trode vacuum tube, a variable period circuit tunable over said wide range of frequencies connected across the input electrodes of said second tube and coupled to the output circuit of said first tube, and a condenser linking said circuit to the control electrode of said first tube of such value that the feed-back of energy therethrough is sufficient to produce amplification of the current frequency selected by said circuit to a desirable degree short of oscillation production.

12. A system for the selection and amplification of any one of the current frequencies of a wide range of frequencies including a three electrode vacuum tube, non-selective impedance means for impressing all of the current frequencies upon the input electrodes of said tube, a second three electrode vacuum tube, a variable period circuit tunable over said wide range of frequencies connected across the input electrodes of said second tube, an impedance linking a potential point in said circuit to the control electrode of said f first tube, and a coupling between said circuit and the output circuit of said first tube i including means for controlling the degree of coupling with the tuning of said circuit whereby the energy effect from frequency to frequency on the input electrodes of said second tube is controlled in a predetermined wayV with frequency.

13. A system for the selection and amplification of any one of the current frequencies of a wide range of frequencies including a three electrode vacuum tube, non-selective impedance means connected between the grid and lament of said tube for impressing all of the current frequencies of said range upon the input electrodes of said tube, a responsive device, a variable period circuit tunable over said wide range of frequencies associated with said responsive device and-coupled to the output circuit of said tube, and an impedance means linking the control electrode of said tube to a potential point associatedwith said variable circuit.

14. In a system forselected amplification of alternating current of any one frequency ingY and transferring energy ofjany one of the desired current frequencies which consists infuori-selectively impressing the currents on theinput of the. first device, selectively ab'- sorbing energy from/the output currents of the rst device and impressing it upon the input ,electrodes of the second device, and impressing a portion of said rselectively absorbed energy on the input electrodes of the first device throughA a path independent of the latter.

.1n testimony whereof I aix my signature.

lSIDNEY Y. WHITE. 

